The gym was blacker than the inside of a cave. (I Know What you Bid Last Summer, Harris, page 10 paperback)

The main character is inside a storage room, looking out into a gym, where the lights have gone out. This is meant to be an exciting simile, and I assume it succeeds at that. The gym was so black!

But is it describing?

1. The gym was blacker than
2. The gym was blacker than the inside of a cave.

#1 tells me the gym was black. How much does the inside of a cave add? I've been on a tour inside a cave, and it was well lit. I know the author didn't mean that, but only because I already know what the author was trying to say without the cave comparison.

At one point in my cave tour, the lights were turned off and I couldn't see a thing, not even my hand in front of my face. Suppose the author was referring to that experience. That's quite a powerful image! However, it's impossible for anything to be blacker than when all of the lights are out inside a cave. Hyperbole, I guess, but why not as black as the inside of a cave?

I have now thought more about this simile than the author. You might say I am thinking too much about the simile, and you are welcome to your opinion and you have company. But when I analyze John Hart's metaphoricals, I'm impressed at how much he thought about them, and I sometimes see more than I did on the first reading.

And you are welcome to enjoy reading moody metaphoricals that don't actually describe, and you can write them and have a lot of company in that too. Your reader is very unlikely to consciously notice any problem. (They are unlikely to consciouslly notice most problems in writing.)

But, in my opinion, metaphoricals that don't describe give a dullness to a book; nothing in the story is ever quite as exciting as it could be. They are kind of like plot and character inconsistencies.

How much did the author NOT think about this cave simile? The readers were already told that the lights were off, so they already knew the gym was dark. When I imagine a gym with the lights out, I don't expect it to be too dark, because I imagine the Exit signs staying lit. So this cave simile could have been telling me that even the Exit signs are off.

Except the Exit signs were on. Also (surprise!) it was light enough to see:

I squeezed out and raced toward the glowing exit sign nearest to me....My eyes had adjusted to the dark enough that I managed to leap over a pile of ski poles without slowing.

So this cave simile is worse than useless for description, it's even misleading. Inconsistencies of any kind undermine the reading experience.

The trawler plunged into the angry swells of the dark, furious sea like an awkward animal trying desperately to break out of an impenetrable swamp. (The Bourne Identity, Ludlum, first sentence)

Impenetrable means the swamp can't be entered, but the trawler is trying to break out. Oops. Second problem, can't all swamps be penetrated? Third, swamps don't have waves, so swamp is an odd image for what the next sentence describes as waves of "goliathan heights".

While we're here, I don't see the point of calling the sea furious; I really do not know the difference between a swell and an angry swell.

Those two examples are extremes. Sometimes the problem is small and simple.

He was being torn in two, torn to shreds. (Lie to Me, Ellison, page 17)

It can't be both.

My advice here is simple. Yes, write that exciting or moody metaphorical. But try making it good for description.

Even Metaphors for Mood Should Describe

Yes, that's a lot of work – it's a lot easier to write a moody metaphorical and not worry about whether it accurately describes.

But the good metaphoricals accurately describe.

Once I clicked on the name Lauren (Mabrey) Leavitt, her life had spilled open like a sack of rice. (Here We Lie, DeBoard, page 132)

No one's coming after you with a sharp wooden stake just because your metaphorical isn't a perfect description. Less than perfect:

I left her laughing. The sound was like a hen having hiccups. (Chandler, Farewell, My Lovely, page 112 paperback)

I don't actually know what a hen with hiccups sounds like. (I suspect, uncharitably, that Chandler didn't know either; I would not be surprised if chickens can't get the hiccups.) Readers are going to imagine different things; Chandler does not have great control of this simile.

So, the descriptive aspect does not score 100%. But it's still descriptive – I know a lot more about her laugh because of that simile. And there was no actual laugh to be accurate about, Chandler's story being fiction and all (and irrelevant to the rest of the story). So this gets a passing score on description. And of course the mood (goofy, funny, creative) was exactly what Chandler and the readers wanted.

Hyperbole is tricky. By definition, hyperbole is not an accurate description at the literal level, and there are more accurate descriptions (by eliminating the hyperbole). But hyperbole still describes, especially as the hyperbole is understood to be figurative, and it shows mood:

She carried a black imitation purse the size of a Buick... (Cairre, page 2)

The narrating character was amazed by the size of her purse. But:

I squeezed out and raced toward the glowing exit sign nearest to me. It was my holy grail, my path to freedom. (I Know What you Bid Last Summer, Harris)

Holy grail is hyperbole – the author wanted excitement. The exit sign was so important! But holy grail has three or four associations that don't work here, including that it was never found. (As contrasted to, say, being lit up in a dark room.)